Phillipines was American territory before the war. When Japs took it, it was on the list of things America wanted back from dem dare Japs.
After Battle of Leyte Gulf wiped out the remnants of the IJN, Japan was fighting a useless war in the name of the Emperor. Pretty unimportant, but it was messy. Terrible Japanese reconnaisance, and underestimation by Allied forces spelled an engagement where neither side was prepared for each other.
I'd say the Japanese complete defeat at the Philippines started at Luzon Battle.
Well, I was actually asking you. You seem to be the expert here on WWII.
Ah, thank you for this wonderful title. My opinion on this is that the Phillipines were one of several retakings, and not the most important one either (I'd put it in 4th most important; smaller than Indonesia, Indochina, and far less important to the Japanese than Manchuria or Korea and about the same size as Burma-Azai Hind and Thailand)
In terms of turning points, all these were just operations when victory was already in sight and clasp; the Solomon Islands and New Guinea were the points where Japan could not go on more. To be frank, the Solomon Islands was a half-assed effort by Japan, but New Guinea was the serious loss for Japan, and slowly from there, the Allies slowly took Indonesia and pushed back Japan.